我在哪里可以在magento中声明我的自定义函数

<?php
namespace MyCompany\MyModule\Model;

class CustomFunction
{
    public function myCustomFunction($param1, $param2)
    {
        // 在这里编写您的自定义函数代码
        $result = $param1 + $param2;
        return $result;
    }
}

<?php
namespace MyCompany\MyModule\Controller\Index;

use Magento\Framework\App\Action\Context;
use Magento\Framework\View\Result\PageFactory;
use MyCompany\MyModule\Model\CustomFunction;

class Index extends \Magento\Framework\App\Action\Action
{
    protected $_customFunction;
    protected $_pageFactory;

    public function __construct(
        Context $context,
        CustomFunction $customFunction,
        PageFactory $pageFactory
    ) {
        $this->_customFunction = $customFunction;
        $this->_pageFactory = $pageFactory;
        parent::__construct($context);
    }

    public function execute()
    {
        $result = $this->_customFunction->myCustomFunction(2, 3);
        echo $result;
    }
}